What is the difference between heavy calcium and light calcium in plastics?

Calcium carbonate is divided into heavy calcium carbonate and light calcium carbonate, both are widely used in plastics, rubber, paper, paints and coatings and other industries, but because of its particle size and surface effect of some differences, so there are some differences in the use of the effect, both have mutual advantages and disadvantages.
In recent years, with the continuous improvement in the level of heavy calcium production technology, heavy calcium carbonate both in the fineness index and particle size distribution have been improved, the superiority of heavy calcium carbonate in the use of plastic products is slowly reflected, especially plastic masterbatch and PVC products, more and more plastic factories from the original use of light calcium technology to the use of heavy calcium technology, to ensure product quality, not only reduce the The cost has been reduced and the production efficiency has been improved.

Differences in crystal structure and stacking state

The particle size of ordinary light calcium is date shaped when fully dispersed, with a long diameter of about 5 to 12 μm, a short diameter of 1 to 3 μm and an average particle size of 2 to 3 μm. However, without surface treatment, after the light calcium is generated and dehydrated and dried, many particles often coalesce together to form large clusters of particles, so the quality of light calcium in the national standard is only 125 μm and 45 μm sieve residue to judge, which does not reflect the true size and distribution. This does not reflect the true particle size and distribution.
After the crushing and grading of ordinary heavy calcium carbonate, although the particle shape is irregular, the particle size is more uniform and the dispersion is better. The cumulative distribution of the particles can be tested by the laser particle size distribution instrument and different specifications can be distinguished according to the size of different average particle sizes.

Light calcium particles pile up more fluffy, pile density is smaller, reflected in a larger sink volume (2.4-2.8mL/g), while heavy calcium carbonate particles pile up more dense, pile density is larger, reflected in a smaller sink volume, heavy calcium carbonate sink volume (1.1-1.4mL/g). So the same weight of light calcium and heavy calcium, light calcium packaging to appear to be a larger package than heavy calcium. But in fact the real difference in density between light and heavy calcium is not so great. The real density of calcium carbonate is reflected by filling the plastic, 400 mesh of heavy calcium carbonate replaces light calcium filled with plastic and the specific gravity increases by about 5-6%, while with 2000 mesh of heavy calcium carbonate, the difference in density is 1-2%.

Oil absorption value

Filled with plastic calcium carbonate whether it is heavy calcium carbonate or light calcium, as the plastic belongs to organic polymers and calcium carbonate belongs to inorganic compounds, the compatibility of the two is not good, in order to make calcium carbonate can be filled with the plastic to have better compatibility, in the mixing process are required to organic treatment of calcium carbonate, the general use of treatment agents are plasticizers (such as DOP, epoxy oil, white mineral oil, etc.), lubricants (paraffin, stearic acid or stearate), coupling agents (titanate or aluminate), etc., the higher the oil absorption value, the need to add. The higher the oil absorption value, the more processing agents need to be added. Due to the high price of activation agents, the filled calcium carbonate powders have better processing properties with low oil absorption values.

Heavy calcium carbonate generally has a lower oil absorption value than light calcium by about 10-15 degrees, and replaces light calcium in plastic formulations by the same proportion, reducing the amount of activation aids used.

Production efficiency

Due to the fluffy nature of light calcium, when filling products such as pvc products, the filling ratio exceeds a certain limit, it is easier to produce a 'bridge' phenomenon in the hopper, which is what we commonly see when the material is not smooth. This has a serious impact on production efficiency. The heavy calcium carbonate, on the other hand, due to the loose particles, mixed with pvc materials after the liquidity is better, the same filling ratio, as light calcium will not be in the hopper to produce the 'bridge' phenomenon.

Brittleness issues

As heavy calcium particles are loose and irregularly shaped, they are combined with plastic polymers with low stress and brittle products.
The same proportion of calcium carbonate filled plastic products, light calcium filled plastic products flexibility than heavy calcium filled.